In the manufacture of steel, molten steel is poured from a metallurgical furnace into a ladle. In pouring the liquid metal from the metallurgical furnace, there is typically some carryover of slag from the furnace into the ladle. The molten steel may also undergo further refinement in the ladle. In this respect, various slag-forming constituents may be added to the liquid steel in the ladle to aid in the refinement process. Thus, the ladle will typically contain molten steel with a layer of slag floating on top of the steel.
The molten steel typically is cast, i.e., drained, from the ladle through a well block in a bottom of the ladle. A slide gate or stopper rod serves to open a channel through which the liquid metal exits the ladle. During the casting process, slag particles can become entrained in the stream of liquid steel exiting the ladle. Entrainment can be caused by vortexing, i.e., swirling, in the vicinity of the well block. Vortexing may occur once the level of the liquid metal in the ladle drops to a critical level. The level of steel in the ladle will eventually drop to a point where slag may also be pulled directly into the stream of liquid steel exiting the ladle, even in the absence of vortexing. The slag particles cause contamination of the liquid metal thereby causing the resulting steel to be of lower quality.
To avoid contamination of the steel by slag, casting is generally terminated before the level of liquid metal in the ladle reaches the critical level at which slag may be entrained. This results in a certain amount of liquid metal being left in the ladle. This residual liquid metal represents lost production, and is referred to as a “decrease in yield.” To increase yield, steelmakers endeavor to allow the level of the liquid steel in the ladle to fall to as low a level as possible before stopping the casting operation.
The present invention provides a ladle bottom that increases the yield of slag-free steel from a steel-making ladle and reduces the entrainment of slag into the stream of liquid metal.